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In the beginning of this passage, the author made a lot of statement to define the distinctive between the shape of nature and city. In his eyes, the difference is acute. Nature moves in circle; Art in straight lines. The nautur is rounded, but the artificial is made up of angles. It's very apparent to see that O.Henry took great resentment at those who change the rounded nature into those straight lines of city street and architecture, the rectangularity of its law and social customs, the undeviating pavements, the hard, severe, depressing, uncompromising rules of all its ways. On the one hand, the constructors of a city change the nature's origin. But on the one hand, the samely modern city also made the two feudists forget their profound hatred. So we can't simply to make conclusion that this article is a irony to those who destroy the harmony of nature for building city. To change the circle of nature into a square shape is to stop the circle of two families' endless hatred.